HIGHSPIRE, Pa. — Speed limits on more than 100 miles of two interstates in Pennsylvania will rise to 70 mph for the first time this summer, with similar increases possible next year on other stretches of roads around the state, state transportation officials said today. The Pennsylvania Department of Transportation's announcement comes a day after the Pennsylvania Turnpike Commission raised the speed limit on a 97-mile stretch of I-76 in central and eastern Pennsylvania from 65 mph to 70 mph. About three dozen states already have speed limits of 70 mph or higher. The sections of interstate where speed limits will rise next month include 88 miles on Interstate 80 in northern Pennsylvania's Clearfield and Clinton counties and 21 miles of Interstate 380 in northeastern Pennsylvania's Lackawanna and Monroe counties. The changes are to take effect the week of Aug. 11. The sections of highway were selected because they provide a blend of urban and rural environments that will allow engineers to study the varying effect of the increased speed limits on crash history and work zones, Transportation Secretary Barry Schoch said. Other highways where the speed limit is 65 mph could see increased limits next spring or summer, Schoch said.